The painting, discovered in the attic of Dorchester’s Mather Elementary School, had hung on the wall of Boston’s historic Parkman House for years. It was one of Mayor Thomas M. Menino’s favorites — a landscape of a sleepy Vermont town nestled in snow — but he knew little more about it than the artist’s name, Aldro Hibbard.

So the mayor did as any self-respecting American with a taste for the thrill of unearthing secret treasure would do: He took his find to “Antiques Roadshow.”

Menino and more than 6,000 people from around the country came to the Boston Convention and Exhibition Center Saturday for a chance to appear on the PBS television ­series in which regular joes learn the history and monetary value of prized family heirlooms and yard sale castoffs.

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Inside a room the size of an airplane hangar, hundreds waited in lines radiating from a central temporary studio: one for jewelry, another for posters and prints, more for furniture, military memorabilia, musical instruments, pottery, porcelain.

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Menino’s wife, Angela, brought her own piece to be ­appraised, a vase, brought to the United States from East Asia in the early 1900s and left to her by a longtime friend. ­Appraiser Lark Mason explained that the vase was ­Japanese, Kutani porcelain, worth about $400 to $600.

“I have a nice cabinet that I’ll display it in,” Angela Menino said.

As the mayor waited for the appraisal of his painting, he was approached by the show’s host, Mark L. Walberg; no, not Mark Wahlberg
, but a celebrity in his own right for the dozens of adoring fans who asked him for autographs.

After studying Menino’s painting, appraiser Colleene Fesko announced that it was quintessential Hibbard, known for his soulful depictions of ­Vermont and Cape Ann.

“It’s a checklist of everything you want to see in a Hibbard: There's the covered bridge; there’s the snow; there’s the sleigh,” Fesko said.

Menino said he liked the painting because of the elegant contours and shadows in the snow. Fesko said Menino’s judgment was right on point.

“Some artists, when they paint snow, you see white paint,” Fesko said, paraphrasing an art critic from 1918. “When you look at an Aldro Hibbard, you see snow.”

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Because it had been framed behind glass, Fesko said, it had maintained excellent quality.

Estimated value: $50,000. But Menino said he had no plans to sell it.

“It’s going back where it came from,” Menino said, “but I’m going to insure it.”

Saturday’s crowd included both first-timers and “Antiques Roadshow” groupies. Tickets were free, but only available through an online lottery. Bill Heron
, 58, of central New York said he had asked 25 friends and family to enter the lottery on his behalf. Only one of them had scored a pair of tickets.

Items up for appraisal ran the gamut: Boston-made decorative porcelain jugs, an original poster from the Beatles’ “Yellow Submarine,” a Norwegian trunk given to 67-year-old Wanda McNamara of West Chesterfield, N.H., when she was a teenager.

But there were duds, lots of them.

Sandi Petri of San Francisco had high hopes for a camera her father had brought from Germany after World War II.

“I made this long haul to be told that I should put the camera on my shelf and enjoy it,” said Petri, chuckling. The camera was worth $20.

For some, the excitement came with the hopes of getting on television, by whatever means necessary.

“We were dead center in the background as they filmed one of the appraisals,” said Rachel Scotch, 41, of Boston, “so we know we’re definitely going to be on TV.”

Somerville residents Dave Sakowski and his wife, Jen Godfrey, brought in a first edition copy of Ernest Hemingway’s “The Old Man and the Sea” that they had purchased from a thrift store near their home for $1.

The appraiser had good news for them: It was worth $500.

They had hoped for a similar coup with their 1958 Gibson Les Paul Junior guitar, inherited from Godfrey’s father. It was a revered brand of instrument, but worn out after years of rock ‘n’ roll, and valued at $500.

The guitar would have been worth much more if it had stayed in pristine condition, the appraiser told them.

But, he told the couple, what’s the fun in that?

Martine Powers can be reached at mpowers@globe.com. Follow her on Twitter @martinepowers.